Huawei Liu

A substrate-engineered WSe ₂ /HfO ₂ /Si PN phototransistor enables programmable positive, negative, and zero photoconductance under near-infrared light for reconfigurable in-sensor neuromorphic computing.

2D semiconductors offer a promising platform for next‐generation integrated circuits and large‐scale electronic systems. Realizing high‐performance p‐type transistors, however, remains challenging due to Fermi‐level pinning, high contact resistance, and poorly defined interfaces in conventional stepwise fabrication. Here, we demonstrate a single‐step tellurization growth strategy that simultaneously forms PtTe ₂ contacts on 2H‐MoTe ₂ channels to directly realize 2D semiconductor transistors. This approach forms PtTe ₂ /2H‐MoTe ₂ metal/semiconductor arrays with precise control of the MoTe ₂ phase at the PtTe ₂ electrode interface, while providing integrated van der Waals metallic contacts without the need for post‐growth of metal contacts. Using this method, we achieve wafer‐scale heterophase arrays characterized by uniform patterning and well‐controlled 2H/1T' phase transformation dynamics. The heterojunctions display sharp and clean interfaces, as verified by TEM, STEM, and EDS mapping. Transistor arrays fabricated from these heterophase structures show Ohmic contacts with low Schottky barrier heights, delivering on/off ratios up to 5 × 10 ⁴ and consistent mobility of 5–9 cm ² /Vs across 100 devices, ensuring efficient carrier injection. Our results establish a scalable pathway for the direct growth of 2D semiconductor transistors, overcoming conventional multi‐step device fabrication bottlenecks and providing a promising platform for large‐scale, and reproducible 2D electronics.

Anisotropic 2D layered materials with distinctive anisotropic electronic band structures and optical response are promising for practical applications in polarization imaging and sensors. Nonetheless, many of the currently reported polarized photodetectors based on anisotropic 2D materials are constrained by the low polarization responsivity and low linear dichroism ratio. Here a high‐performance polarization‐sensitive photodetector based on the novel in‐plane anisotropy 2D violet phosphorus (VP) crystal is reported. The angle‐resolved polarized Raman spectroscopy (ARPRS) study and the anisotropic electrical transport measurements revealed the highly in‐plane anisotropy phonon vibration and electrical properties of VP crystal. The anisotropic ratio of electron mobility is calculated to be 2.7 at room temperature. Moreover, a polarization‐sensitive photodetector based on the VP nanosheet shows high photoresponsivity of up to 341 A W⁻¹ and a linearly dichroic ratio of up to 3.9, which is much larger than most other anisotropic 2D materials. These results indicate that the anisotropic VP crystal would be suitable for polarization‐sensitive photodetectors, which leads to a promising perspective for future novel electronic and optoelectronic devices.

Small contact resistance and low Schottky barrier height (SBH) are the keys to energy-efficient electronics and optoelectronics. Two-dimensional (2D) semiconductors-based field effect transistors (FETs), holding great promise for next-generation information circuits, still suffer from poor contact quality at the metal—semiconductor junction interface, which severely hinders their further applications. Here, a novel contact strategy is proposed, where Bi₂Te₃ nanosheets with high conductivity were in-situ epitaxially grown on MoS₂ as van der Waals contacts, which can effectively avoid the damage to MoS₂ caused during the device manufacturing process, leading to a high-performance MoS₂ FET. Moreover, the small work function difference between Bi₂Te₃ and MoS₂ (Bi₂Te₃: 4.31 eV, MoS₂: 4.37 eV, measured by Kelvin probe force microscopy (KPFM)), enables small band bending and Ohmic contact at the junction interface. Electrical characterizations indicate that the MoS₂ FET device with Bi₂Te₃ contacts possesses a high current on/off ratio (5 × 10⁷), large effective carrier mobility (90 cm²/(V·s)), and low flat-band SBH (60 meV), which is favorable as compared with MoS₂ FET with traditional Cr/Au electrodes contacts, and superior to the vast majority of the reported chemical vapor deposition (CVD) MoS₂-based FET device. The demonstration of epitaxial van der Waals Bi₂Te₃ contacts will facilitate the application of 2D MoS₂ nanosheet in next-generation low-power consumption electronics and optoelectronics.

Semiconducting p-n heterojunctions, serving as the basic unit of modern electronic devices, such as photodetectors, solar-energy conversion devices, and light-emitting diodes (LEDs), have been extensively investigated in recent years. In this work, high performance self-powered broadband photodetectors were fabricated based on vertically stacked p-n heterojunctions though combining p-type WSe2 with n-type Bi2Te3 via van der Waals (vdW) epitaxial growth. Devices based on the p-n heterojunction show obvious current rectification behaviors in the dark and superior photovoltaic characteristics under light irradiation. Maximum short circuit current of 18 nA and open circuit voltage of 0.25 V can be achieved with the illumination light of 633 nm (power density: 26.4 mW/cm2), which are among the highest values compared with the ever reported 2D vdW heterojunctions synthesized by CVD method. Benefiting from the broadband absorption of the heterostructures, the detection range can be expanded from visible to near-infrared (375-1550 nm). Moreover, ascribing to the efficient carriers separation process at the junction interfaces, the devices can be further employed as self-powered photodetectors, where fast response time (≈210 μs) and high responsivity (20.5 A/W at 633 nm and 27 mA/W at 1550 nm) are obtained under zero bias voltage. The WSe2/Bi2Te3 p-n heterojunction-based self-powered photodetectors with high photoresponsivity, fast photoresponse time and broad spectral response will find potential applications in high speed and self-sufficient broadband devices.

Semiconductor heterostructures are basic building blocks for modern electronics and optoelectronics. However, it still remains a great challenge to combine different semiconductor materials in single nanostructures with tailored geometry and chemical composition. Here, a polar-induced selective epitaxial growth method is reported to alternately grow CdS and CdSxSe1-x heterostructure nanoribbons (NRs) side by side in the lateral direction, with the heterointerface (junction) number to be well controlled. Transmission electron microscopy (TEM) and spatial-resolved µ-PL spectra are employed to characterize the heterostructure NRs, which indicate that the achieved NRs are high quality heterostructures with sharp interfaces. Kelvin probe force microscopy (KPFM) and femtosecond pump-probe characterizations further confirm the efficient charge transfer process across the interfaces in the multi-junction NRs. Photodetectors based on the achieved NRs are realized and systematically investigated, demonstrating junction-number-dependent optoelectronic response behaviors. NRs with more junctions exhibit more superior device performances, reflecting the important roles of the high-quality interface regions. Based on this multi-junction NRs device, high on-off ratio (107) and remarkable responsivity (1.5×105 A/W) are demonstrated, both of which represent the best compared to the ever reported CdS, CdSe and their heterostructures. These novel multi-junction NRs may find broad applications in future integrated photonics and optoelectronics devices and systems.